Electronic controller



Oct. l1, 1955 J. LEGNARO 2,720,612

ELECTRONIC CONTROLLER original Filed Dec. 13, 1945 v GI LLI D CII F-O O LLI (I 5 Sheets-Sheet l JOHN L. LEONARD BY my z W TORNEYS OC. 11, 1 L LEONARD ELECTRONIC CONTROLLER Original Filed Dec. 13, 1945 5 Sheets-Sheet 2 No m u Ow-v RA, o

W l0 :f r\ "TE:

ma j So I D v L? a D l v l Mov-1 I Il N 2^ g rf 14j-: 'f5 o INVENTOR.

JOHN L. LEONARD ATTORNEYS 0ct. 11, 1955 J. L. LEONARD 2,720,612

ELECTRONIC CONTROLLER original' Filed D60. 13, 1945 5 Sheets-Sheet 3 f n" fr--n--n--Hm- V57 JZ IN V EN TOR. JOHN L. LEONARD Oct. 11, 1955 .1. LEONARD 2,720,612

ELECTRONIC CONTROLLER Original Filed Dec. 13, 1945 5 Sheets-Sheet 4 WIMMMMMK V63 ZZZ-m V V- IN VEN TOR. JOHN L. LEONARD BY g y z A OR/VEYS Oct. 1l, 1955 J. L. LEONARD 2,720,612

ELECTRONIC CONTROLLER Original Filed Dec. 13, 1945 5 Sheets-Sheet 5 F fg. 5

IN V EN TOR.

JOHN L. LEONA H0 A TR/VEYS t atented Get. 11, 1955 ELECTRONIC CONTROLLER John L. Leonard, La Mesa, Calif., assigner to the United States of America as represented by the Secretary of the Navy Original application December 13, 1945, Serial No. 634,844, now Patent No. 2,666,098, dated January 12, 1954. Divided and this application June 10, 1952, Serial N o. 295,222

3 Claims. (Cl. 315-166) My invention relates to measuring of equipment and more particularly to methods of and means for adjusting a measuring device having a relatively small range of operation to measure signals having a relatively large range of volume.

It is frequently desirable to use a highly sensitive device such as a vacuum tube amplier for purposes of measuring signals having a large variation in level. Unfortunately, however, the vacuum tube amplifier is not completely satisfactory for this purpose for the range of signal levels for which the vacuum tube amplifier constitutes an accurate measuring instrument is relatively small. For instance, in the application of a signal measuring system to test propagation of underwater sound waves it is necessary to indicate the level of signals varying over 90 decibels Whereas the response of a good vacuum tube amplifier and recording galvanometer is accurate only over about 25 decibels. Under these circumstances, the vacuum tube amplifier is relatively ineifective for it can only accurately measure the level of incoming signals over a 25 decibel portion of the total 90 decibel range.

One method of avoiding the above mentioned difficulty is to provide a variable attenuating device in the input circuit of the amplier so that the level of input signals may be adjusted to a value wi Lin the 25 decibel amplier range. The true level of incoming signals will then correspond to the combination of the artificially introduced attenuation and the signals as measured by the amplil'ier. vvV`nile this method satisfactorily increases the range over which the amplier may be used as a measuring instrument, it requires that two readings be made instead of a single reading and in addition demands the attention of an operator` fhere it is desired to avoid the need of an operator or to record a minimum number of readings, this method is not satisfactory.

I have discovered that the disadvantages associated with the use of external attenuator in conjunction With an amplifier may be avoided by arranging the attenuator to be automatically actuated in predetermined steps as the level of the incoming signals vary. A record may be made of the changes in attenuation and this record, together with a record of the amplier output provides an accurate indication of the level of incoming signals even though the incoming signals vary greatly in magnitude.

In accordance with another aspect of my invention, the automatic change in attenuation associated with a change in level of incoming signals is delayed for a predetermined time. This prevents the attenuation from responding to short time irregularities in the level of the incoming signals, thereby preventing confusion in the resulting record and facilitating interpretation of the data obtained.

In accordance with a further aspect of my invention, the automatic changes in attenuation are made in predetermined steps which may be accurately established at equal values. It then becomes unnecessary to make an exact record of the operation of the attenuator inasmuch as the step-by-step changes constitute the entire information to be recorded. In fact, it is readily possible to provide a single record sheet on which both the output of the amplier and the position of the attenuator is shown.

While the invention is susceptible of various modifications and alternative construction, I have shown in the drawings and will herein describe in detail the preferred embodiment. It is to be understood, however, that I do not intend to limit the invention by such disclosures for I aim to cover all modifications and alternative construction falling within the spirit and scope of the invention as defined in the appended claims.

In the figures:

Figure 1 is a perspective view showing the mechanical components of my invention.

Figure 2 is a schematic diagram showing the circuit of my invention.

Figure 3 is a diagram showing how my circuit responds to incoming signals in excess of the predetermined value.

Figure 4 shows how my invention responds to signals below the predetermined value.

Figure 5 is a schematic diagram of the electro-mechanical portion of my invention.

Referring now to Figure 1. Attenuators 1 and 2 comprise resistances operated by gears 3 and 4 and half gear 5 connected to shaft 6. Gears 3 and 4 and half gear 5 are arranged so that for a complete revolution of half gear 5 attenuators 1 and 2 are successively rotated over their entire range of rotation. Shaft 6 is attached to synchro transmitter S which in turn is connected to a repeater and recording mechanism. In addition, sprocket 7 is attached to shaft 6 and adapted to be rotated by chain 9. Sprocket 10 operates chain 9 and is in turn actuatedby Geneva gear 11 attached to a gear train to which series wound motor 12 is connected. Hence, when motor 12 rotates over a predetermined angle, Geneva gear 11 rotates bracket 10 one notch and attenuator 1 or attenuator 2 is correspondingly changed.

By the use of Geneva gear 11, I am enabled to obtain a highly accurate rotation of sprocket 1l) even though I do not control the exact angular position of motor 12. Hence, by approximate control of motor 12 I am enabled to obtain a change in attenuation of accuracy adequate for measurement. By causing motor 12 to be actuated by the presence of amplilier output signals above or below predetermined levels, I achieve an automatic change in attenuation having a high degree of accuracy and which restores the signals to the desired operating range of the ampliier.

Figure 2 shows a detailed circuit diagram of the electronic portion of my invention. In the diagram, 13 is a vacuum tube having its grid connected to the input signals desired to be measured, The cathode of tube 13 is grounded through cathode bias resistance 21 and the anode connected to a source of positive voltage through resistances 23, 22 and adjustable resistance 38. By-pass condenser 59 provides a low impedance path to high frequency current around resistance 38. The anode of tube 13 is connected by coupling capacitor 52 to the anode of the rst section of duplex diode 14. The cathode of the lirst section of tube 14 is connected by resistance 25 and by-pass condenser 53 to ground. The anode of tube 14 is connected to ground by resistance 24. The common connection between resistors 22 and 23 is connected by coupling capacitor 51 to the anode of the second section of tube 14 and to resistance 27. The cathode corresponding to this anode is connected to ground by resistance 26 which is by-passed by condenser 54. Tube 15 comprises a grid controlled gas discharge tube having its control grid connected to the cathode of the second section of tube 14 and its anode connected by resistances 31, 32 and 33 to a source of positive potential. 15'is connected to ground by resistance `28 `and tothe the .received pulses.

andere The cathode of tube source of positive potentialrby resistances 29 and 30, which provide adjustable positive cathode bias. Condenser 55 is connected between the cathode of tube 15 and the common connection between resistances 31 and 32. The common connection between resistances 32 and 33 is connected by means of coupling capacitor 56 to .the cathode of the tirst section of tube 16 and the anode of the second section. The anode of the lirst section of tube is connected directly to ground whereas the `cathode ofthe second section is connected to the grid of gas ,discharge tube 17 and by coupling capacitor 57 to the cathode thereof. Resistance 34 .connects the grid of tube .17 to ground. The cathode vof tube .17 .is connected .to ground by resistance 35 and to the source of'positive potential by adjustable resistance 3'6. This .provides adjustable grid bias `to tube 17. The anode of tube .'17 .is connected to one of the control :relay terminals 59. The otheL-terminal 59 is connected by resistance V37 to the source of positive potential and by condenser 58 to the Y cathode.

. Considering now the circuit through tubes ,1819'and 20. The grid of gas discharge tube 18 is connected to the cathode of the iirst section of tube V14. The Vanode Yof tube :18 vis connected by resistance 45 to the :source of positive potential. The cathode of tube 18 is lconnected by .resistances 39, 40 and 41 to ground and the common connection of resistances 39 and 40 connected by resistance :42 and adjustable resistance 43 tothe positive 'source -of potential.Y This provides adjustable cathode and fthe cathode of the second-section. The cathode of A the iirst section of tube -19 is connected directly to ground Y whereas the vanode of the second section Vis connected to the vgrid of gas discharge tube 20. The grid of tube is .connected by resistance 44 to an adjustable voltage determined by the voltage divider action of resistances 47 discharges through resistance 31 and tube 15. Inasmuch as 'the resistanceof resistances 32 and /33' as well as'thev cathode resistance 28 is made very large,tthe currentrow through tube 15 and these resistances is very smallV and when condenser 55 relatively discharged, inadequate potential is available to cause current flow through tube 15 and conductiontherethrough accordinglyceases. time, the grid of tube 15 again gains control and condenser .55'sloWly 'charges up to thefull Vvalue of 'the direct potential supply. This cycle for thepulses ofEigure`3, curve I, is shown in Figure 3, curve III, which shows the voltage across condenser 5'5. Inthe case ofithe Apulses exceeding the tiring value of tube 15, condenser v55 rapidly discharges until current ftlow lin 4tuhe .-15 ceases.

'Thus the terminal voltage of condenser 55 Vis rapidly're-v Y duced to a low value. Condenser 55 then charges at-a relatively slow rate, reaching a fully charged condition by the time the next pulse comes along. VThe voltage across condenser 55 therefore constitutesa series of sudden dips corresponding to the pulses applied to the -input terminal 67 which are .above ,the tiring level of tube .15 and a series of relatively slow voltage increases corresponding to the charging action through resistances 28, 32 and 33.

When charging current flows through resistance 33 Ato condenser 55, the cathode of the rst section of tube 16 is made negative with respect to the anode. Current ow then takes place until .condenser 56 is discharged kby the amount of the voltage drop in resistance 33. When Itube 15 ceases to conduct, the voltagedrop throughresistance Y condenser `57 is very long in respect Vto the time intervalY and 48. This provides an adjustable grid bias for tube v in .Figure 2 kwith respect to the maximum level 'control relay connected to terminals 59. The input fat terminals 67 `comprises l-a succession of pulses the amplitude of which it is .desired to measure. These .pulses may becharacteristie :of -the :signals or may be obtainedV by 'actuating the amplifier only Vat .predetermined intervals. Figure 3, curve .1, shows a group of these pulses. When these pulses are :applied to the grid circuit of tube 13, -a plate current changertakes place. This causes condenser 51 to discharge through :thesecond section fof diode 14, thereby producing a succession of voltage pulses across resistance 26. As shown inFigure 3, curve II, the magnitude of these, pulses varies in accordance with the magnitude of pearing across resistance 26 produces grid bias on tube 15 ,1he `latter tubeis .actuated in accordance Vwith themagnitude Jof the pulses.

inasmuch as .thevoltage drop ap-V VIf vthe pulse is such that voltage acrossresistance V26 vis suticien't to cause 'gas discharge Y tube :Q15 to conduct, current will ow in the llatter tube. On the other hand, if the Yvoltage Vacross resistance 26 .due

tothefpulse of current through tube 14 vis not adequate to 33 disappears rand condenser`57 is charged through theV second .section of tube 16. This current flow `is shown in Figure 3, curve lV. This charging tendency corresponds to the total voltage drop in 'resistance 33 whenV condenser v discharges through tube 15 and is indepen-V dent of the magnitude of the initial -pulse appearing at terminal 67 so longas that pulse lires tube 15. Inasmuch as the time constant corresponding to vresistance 34 and between pulses, condenser 57 is charged an equal amount of 'each pulse above the level, Vthereby producing a stepped voltage at condenser 57 and the grid of -tube 17. This is shown in Figure 3, curve V.

The curves ofr Figure V3 are based on a succession ofvoltage pulses above the maximum level which occur at short intervals. :In the -event thatrtwo pulses above the maximum level are spaced Vby a considerable period of time, condenser 57 will discharge through resistance .34 toa significant degree. :Hence the voltage pulses, :to actuate tube 1'-7,V must be .closely spaced, the spacing being determined by the time constant of .condenser-57 Aand resistances 34 and 35. By adjusting the value of these resistances, I cause the system :to respond .to .the particular predetermined value `below the ring'voltage. This .point Y may be varied by selection of the size 57,134,135, and'37.

Ina'smuch as the current flow in tube 17 passes Vthrough f the level control relay, the mechanical system is actuated to lincrease .the attenuation. Gas discharge tube 17 automatically restoresritself to the quiescent condition when condenser 58 discharges inasmuch as the'.

resistance 37 is so large `that ktube 17 cannot maintain conduction if all the anode current must Vpass therethrough. Y

AConsidering :now the control ofthe Alevel control relay exercised by tubes 18, 19, and 20. :When a Vpulse Vappears at the grid of `tube 13, a plate current increase takes place andthe Voltage drop 'of-resistancesl,

At thisV 23 and 38 is raised accordingly. This causes a voltage to appear across the rst section of ltube 14 and a corresponding current ow through resistance 25. The cathode of the first section of tube 14 swings positive and a positive pulse appears at the grid of gas discharge tube 18. Since the anode of the rst section of tube 14 is connected directly to the anode of tube 13 through coupling capacitor 52, the voltage appearing at the grid of tube 18 is in excess of the value appearing at the grid of tube 1S by an amount depending on the voltage divider action of resistances 38 and 22 in conjunction with resistance 23. It therefore requires a smaller signal pulse at terminal 67 to cause tube 18 to conduct than to cause tube 15 to conduct when the two tubes are adjusted to tire at the same voltage. When tube 18 conducts, condenser 63 discharges through resistance 45, thereby causing condenser 62 to charge through the first section of diode 19 due to the sudden increase of charging current for condenser 63. When condenser 62 is charged and tube 18 ceases to conduct, condenser 64 is partially discharged through the second section of diode 19, condenser 62, and resistances 40, 39, and 46. If signals appear at the input 67 with sutiicient frequency to prevent condenser 64 from ever charging up to a value sufficient to trigger gas discharge tube 20, no current ow will take piace through minimum level control relay connected to terminal 66. On the other hand, if signals fail to come with suicient frequency, condenser 64 will charge to a value adequate to tire tube 26 and current ow therethrough will take place. This current fiow will exist until the charge on condenser 65 is dissipated and the system will then be restored to the initial unenergized condition.

The operation of the circuit through tubes 18, 19 and 20 is illustrated in Figure 4. In Figure 4, curve I, shows a succession of pulses appearing at the input terminal 67. Some of these pulses are above the minimum level shown by the dashed curve and others are below that level. Curve II shows the voltage across resistance 25 corresponding to the pulses, the magnitude of this voltage being proportional to the magnitude or" the incoming pulses. Inasmuch as the gas discharge tube 18 is arranged to conduct when the incoming pulses exceed the minimum level and to fail to conduct when incoming p'ulses do not exceed the minimum level, current flow through tube 18 takes place only when pulses exceeding the minimum level are received. The resulting voltage at condenser 63 is as shown in Figure 4, curve lll. rfhis curve consists of a sudden discharge associated with each of the pulses exceeding the minimum level and a relatively slow recovery to normal voltage after each discharge. This curve is directly analogous to curve lll, Figure 3. The current iiow through the second section of diode 19, and the corresponding current tending to discharge condenser 64, is shown in Figure 4, curve 1V. This current consists of a pulse corresponding to each of the incident pulses which exceed the minimum value. The resulting charge of condenser 64, and the corresponding bias on gas discharge tube 29, is shown in Figure 4, curve V. During the period when successive pulses exceed the minimum value, condenser 64 is repeatedly discharged and the voltage appearing at the grid of tube 2t? consists of a saw tooth wave which never reaches a value sufcient to fire the tube. On the other hand, when a long period wherein no pulses are received takes place, condenser 64 continues to charge until eventually the firing voltage of tube 20 is reached. At this time con duction will take place from condenser 65 through tube 20 and the resulting voltage across R 46 will reset condenser 64 below the firing voltage. The current flow from capacitor 65 will actuate the minimum level control relay and cause the attenuation in the amplifier circuit to be decreased, thereby raising the level of the input signals amplier to the best operating portion of the amplifier range.

`In order to achieve the time delay in operation of my circuit as shown in Figure 2, I provide tubes 17 and 20 with grid bias such that condensers 57 and 64 reach the desired trigger voltages only after a succession of signals from tubes 15 and 18 which persist over the desired time delay. In the case of tube 17, this is accomplished by adjusting resistor 36 which varies the potential of the cathode of tube 17 and hence the value of charge at which condenser 57 will cause the tube to conduct. In the case of tube 20, resistance 47 has a similar function for it changes the voltage applied to condenser 64 and hence the time required for it to charge to the potential wherein tube 20 fires.

Referring now to Figure 5 which shows in schematic form the mechanical elements of my system. Terminals 59 are connected to the operating coil of the maximum level control relay. Contacts 69 and 70 are controlled by current in this coil or release coil 68. Terminals 66 are connected to the operating coil of the minimum level control relay. Contacts 72 and 73 are actuated by this coil and release coil 71. Series wound motor, 74, has its armature, 75, connected to normally closed relay contacts 69 and 72 and normally open relay contacts 70 and 73. The field of this motor is connected through limit switches 78 and 79 to contacts 70 and 73 respectively. The limit switches are opened when the attenuator drive travels beyond its limit in either direction. Gear 77 is connected to motor 74 and drives the Geneva movement 11 which in turn operates chain drive 9 on shaft 6. The latter operates the attenuators, 39, as shown in detail in Figure 1.

When a signal appears at terminals 59, contacts 69 are opened and contacts 70 closed. Current then ows from source 81 through field 76 of motor 74 to limit switch 79, through contacts 7i) to armature 75. Passing through the armature, the current flows to contacts 72 to the opposite side of source 81. Motor 74 therefore turns in a direction corresponding to the armature and field connections. After motion sulicient to operate the Geneva movement 11 takes place, relay release switch 82 is closed. This causes current ow through relay release coil 68, thereby causing contacts 69 and 70 to return to their normal position.

When a signal appears at terminal 66, relay contacts 72 are opened and contacts 73 closed. Current iiow will then take place from source 81, through field 76 of motor 74 to limit switch 78. From there current iiows through contacts 73 to armature 75, and contacts 69 to the opposite terminal of source 81. In this case, however, the direction of current fiow through armature as compared with that when coil 59 is actuated so that the rotation of series wound motor 74 is in the opposite direction. This causes Geneva movement 11 to rotate in the reverse direction, thereby moving attenuator 80 to decrease the attenuation. When Geneva movement 11 has moved, relay release switch 83 is actuated, thereby causing current tlow in the release coil 71 and returning contacts 72 and 73 to their previous positions.

Relay contacts 69 are adapted to be opened by current in actuating coil 59 whereas relay contacts 70 are adapted to be closed by current in coil 59. The construction of the relay is such that it locks mechanically when actuated so that the contacts remain in this position even though current fiow through coil 59 ceases. When switch S2 closes, the locking mechanism in the relay is opened and contacts 69 are closed and contacts 70 opened. Upon subsequent current flow in tube 17, contacts 69 are opened and contacts 70 closed for a sutlicient time by current flow in coil 59 to swing the Geneva star movement 11 beyond the point at which relay release switch 83 is closed. Further motion of the movement takes place until the next closing point of relay 82 is reached. Similarly, contacts 72 and 73 coact with release switch 83 to cause motor 74 to swing Geneva star movement 11 one stop in the reverse direction when tube 20 is fired.

In order to prevent recycling of the mechanical system,

I designr'condcnsers 65 and 58, -Figure V2, Itchave capacity such Vthat tubes -17 an'd'Q/i) cease conduction by the time rela'yfrelease `coils 68 -and -71 :are actuated.

1n the event Vthat -signaisto Vbe amplified are continuous signals notarrivin'g in discrete pulses,-a number of kmethods are avaitable whereby the control operation be Y'done by biasing'a Etube in the amplifier circuit beyond cut-E bias. As an alternative, tube 13 of the gain changer circuit could be provided *with a circuit which gives itV zero grid bias except fat -predetermined instants corresponding to the time when pulses are desired to be applied to `vthe automatic `gain control circuit. v vIn either event,'the `operation of the gain control -circuit is identical with thatdescr'ibedabove. Y

The 'selection fof components for A-my system may be given wide variation. l `doY not intend to be limited by any/particular'va'lues or" the components Within the spirit and scopefof my invention. `Merely Aby Way of illustration,'=however, Vrnayvuse the :followinglva'lues:

v15V-2050 thyratron 16-6H6 vacuum .tube 17-20'50 th-yratron 1'84-'2'050 thyratron. 19-6H6 vacuum tube 20.-'2050 thyratron 21-3300 ohms resistance 2'227,000 ohms resistance 23-6S,000 ohms resistance 24'-1 megohm resistance 25--22 megohms resistance 26-22 megohrns resistance 7.7-1 megohm resistance 2833,000 ohms risestance 29-220,0'00 ohms resistance 30-1 megohm variable resistance 31--4100 ohms resistance B12- 33,000 lohms resistance 33.-820,0'O'0 -ohms resistanceY Y t9-422,000 ohmsresistance f8 50-40 microfara'ds capacity -1-5005 niicrofarad capacity 52-.005 microfarad capacity 53-.'0002 microfarad capacity S4-.0002 microfarad capacity 55-.25 microfarlad capacity SG-l Irnicrofarad capacity 57-1.0 micro'farad capacity 58-2.0 microfarads vcapacity 62`-.0l5 microfarad capacity 6.3-4.25 microfarad capacity 64-2-0 microfarads capacity 6S-2.0 microfarads capacity l claim:V

'1. An electroniccountiug circuit comprising ariirstgrlid controlled gas discharge tu'be 'biased to be rendered conducting upon the application ofsignal pulses above a predetermined level to its grid circuit, a second gas ydischarge" tube normally biased to a non-conducting state, a con-VV enser connected in the grid circuit of saidr second ,gas

discharge tube, and a charging circuit 'for said condenser, Y

said charging circuit including .means Vresponsive to .each conductive periodof said first gas discharge tube to supply a predetermined small increment of charging currentfto said condenser whereby said second gas discharge tubeis rendered conducting when said condenser is Vsubstantially fully charged. 1

2. An electronic counting circuit comprising a fiirstrgr'id Y controlled gas discharge tube biased to be rendered conducting upon vthe application of signal `pulses above 'a predetermined level 'to -its grid circuit, a second grid controlled gas discharge tube normally biased to a non-con-v ducting state, a condenser connected Ainthe grid circuit of said second gas "tube, a charging circuit vfors'a'id condenser connected toa source of electrical potential, said second gas ydiscliarge tube being rendered conducting upon said condenser being lsubstantially fully charged, and means including said iirst gas kdischarge tube operative to partially discharge said condenser upon the occurrence of each 'signal pulseiabove vthe ypredetermined level.

3. An electronic counting circuit comprisinga first grid controlled gas discharge'tube biased to be rendered consaid condenser to the plate of said first gas discharge tube.

References Cited in the Vfile of this patent 'UNITED STAT-Es PATENTS Y 2,185,635 Kock Jan. 2, :1940 2,275,930 Torchcux MaL 110, 1942 2,444,014 Williams June .22, 1948 2,463,318k YSchneider .t .Marx l, 1949V 2,478,907 Edgerton V Aug. 6, 1949 2,533,567 1950 Erickson Dec. 17, 

